Applying organic crystals having non-linear optical effects as terahertz-wave generating elements or terahertz-wave detecting elements has been studied.
In general, the intensity of terahertz waves generated from non-linear optical crystals varies depending on frequencies, but the frequency range in which the intensity of the terahertz waves is lowered varies depending on the type of compounds constituting non-linear optical crystals. In this regard, there is proposed a technique in which plural kinds of substituted phenylsulfonate providing crystals having different ranges in which the output is lowered are combined with respect to a non-linear optical crystal containing a salt of pyridinium and substituted phenylsulfonate so that terahertz waves with a sufficient output intensity are generated in a wide range (for example, Patent Literature 1).